The overall objective of the proposed work is to develop an on-site screening method for the enumeration of fungal spores and bacteria in air samples. It is proposed that air sampling be carried out with a size- selective device upstream form an appropriate membrane filter disc with subsequent analysis by a combination of visible and fluorescent microscopy. The primary goal of the analytical methods development effort will be to produce an analysis protocol that can be used in the field and that will yield results within minutes of the cessation of air sampling. Enumeration of fungal spores and bacteria will be accomplished by supravital staining organisms with fluorescent probes and then observing them by epifluorescence microscopy and, if possible, by transmitted light microscopy. The air sampling device will be fabricated to collect primarily thoracic particles (i.e., those particles that pass beyond the head and neck during breathing). Particles will be deposited on a membrane filter that is found to be suitable for microscopic analysis. Test atmospheres of a nonbiological fluorescent aerosol and representative fungal spores will be produced in the laboratory for the evaluation of the sampling and analytical procedure developed. A field evaluation of the effectiveness of the procedure in assessing the potential exposure to airborne biological aerosols that have been associated with increased incidence of pulmonary disease will be undertaken. Total and aggregate counts of fungal spores and bacteria will be compared to results obtained by scanning electron microscopy. Count concentrations will also be compared to results of the culturing of impactor samples. Time/concentration profiles will be generated in a variety of agricultural environments and in an office building.